We Keep Coding

java.sql.Connection not working when import from a different class

I have managed to pinpoint two of the mistakes I had and will therefore update my question.
Firstly, my previous error:
java.lang.ClassCastException: Bootstrap method returned null
was fixed by simply adding this line to build.graddle (app) dependencies:
implementation group: 'com.google.protobuf', name: 'protobuf-java', version: '3.6.0'
So that was nice, However this did not solve all my issues. This is my current register button method:
registerButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
try {
conn = Utils.getConnection();
} catch (Exception e) {
e.printStackTrace();
}
}
});
As you can see I am focusing solely on getting a connection as it seems to be the heart of the problem. In debugging I also modified getConnection() to the following:
public static Connection getConnection() {
String driver = "com.mysql.cj.jdbc.Driver"; //com.mysql.jdbc.Driver doesn't work either
String url = "url";
String username = "user";
String password = "pass";
try {
Class.forName(driver);
} catch (ClassNotFoundException e) {
System.out.println("Where is your MySQL JDBC Driver?");
e.printStackTrace();
return null;
}
System.out.println("MySQL JDBC Driver Registered!");
Connection connection = null;
try {
connection = DriverManager.getConnection(url,username, password);
} catch (SQLException e) {
System.out.println("Connection Failed! Check output console");
e.printStackTrace();
return null;
}
if (connection != null) {
System.out.println("You made it, take control your database now!");
} else {
System.out.println("Failed to make connection!");
}
return connection;
}
And this is the error that I am receiving now:
I/System.out: Connection Failed! Check output console
W/System.err: java.sql.SQLNonTransientConnectionException: Could not create connection to database server. Attempted reconnect 3 times. Giving up.
W/System.err: Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
Caused by: java.net.SocketException: socket failed: EACCES (Permission denied)
I will keep this up to date on further changes. Again, if the issue is obvious I apologize in advance. Thanks for the help!

"Invalid authorization specification" error on UCanAccess connect

I am having a problem with the UCanAccess driver namely that when I attempt to connect to a database using the following code
public static void main(String[] args) {
//establish connection with database in order to execute sql queries
try {
conn = DriverManager.getConnection("jdbc:ucanaccess://H:\\IT_PAT_Program_LOCALONLY\\IT_Pat_Database.accdb;showschema=true");
System.out.println("Connection Established");
} catch (SQLException ex) {
System.out.println("Could Not Connect to database\n"+ex);
}
//closes the database connection at program shutdown
Runtime.getRuntime().addShutdownHook(new Thread() {
public void run() {
try {
conn.close();
System.out.println("Shutdown Succesful");
} catch (SQLException ex) {
System.out.println("An exception occured\n"+ex);
}
}
});
}
I am met with the following error:
Could Not Connect to database
net.ucanaccess.jdbc.UcanaccessSQLException: UCAExc:::3.0.0 invalid authorization specification - not found: Admin
The database is also connected as a persistence unit however since I'm unaware of any way to make use of that from within the code (Google has been no help) this method seems to be my only option.

We can not see where you are doing the authorization in your code.
user ?
password ?
Class.forName("net.ucanaccess.jdbc.UcanaccessDriver");
Connection conn=DriverManager.getConnection(
"jdbc:ucanaccess://<mdb or accdb file path>",user, password);

How to remove this exception while making jdbc example ?

I am creating a simple example of jdbc .I am getting this error .I run my sql server on my mac machine .can you please tell me how to make connection with my sql and remove this error .I already include connector jar file .
Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1129)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:358)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2489)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2526)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2311)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:834)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:416)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:347)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:207)
at HelloWorldExample.main(HelloWorldExample.java:17)
Caused by: java.net.UnknownHostException: local
at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress$1.lookupAllHostAddr(InetAddress.java:877)
at java.net.InetAddress.getAddressFromNameService(InetAddress.java:1230)
at java.net.InetAddress.getAllByName0(InetAddress.java:1181)
at java.net.InetAddress.getAllByName(InetAddress.java:1111)
at java.net.InetAddress.getAllByName(InetAddress.java:1047)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:248)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:308)
... 15 more
Here is my code ..I am using mac
import java.sql.*;
/**
* HelloWorldExample : JDBC Tutorial that creates a simple database, stores in a single row
* and retrieves the data to then be displayed on standard out. The database is cleaned up
* to reduce clutter for this example.
* Author: Kevin Hooks
* Date: April 18th, 2012
**/
public class HelloWorldExample {
public static void main(String[] args) throws SQLException{
// Note that you can use TCP/IP by using this URL
// "jdbc:raima:rdm://localhost"
// The rdmsqlserver must be running to use TCP/IP
Connection Conn = DriverManager.getConnection("jdbc:mysql://local");
try {
Statement Stmt = Conn.createStatement();
try {
try { //Since the database is created here, it cannot be created twice
Stmt.execute("DROP DATABASE hello_db");
} catch (SQLException exception) {}
Stmt.execute("CREATE DATABASE hello_Db");
Stmt.execute("CREATE TABLE hello_table (f00 char(31))");
Conn.commit();
PreparedStatement PrepStmt = Conn.prepareStatement("INSERT INTO hello_table (f00) VALUES (?)");
try { //Sets parameter value to a string
PrepStmt.setString(1, "Hello World!");
PrepStmt.execute();
Conn.commit();
ResultSet RS = Stmt.executeQuery("SELECT * FROM hello_table");
try {
while(RS.next() != false) {
System.out.println(RS.getString(1));
}
} finally {
RS.close();
}
} finally { //Cleans up by dropping database in this case
Stmt.execute("DROP DATABASE hello_db");
PrepStmt.close();
}
} finally {
Stmt.close();
}
} catch (SQLException exception) {
System.err.println("SQLException: " + exception.toString());
}finally {
Conn.close();
}
}
}

The hostname of the loopback address is localhost, not local.

Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at HelloWorldExample.main(HelloWorldExample.java:17)
Line 17:
Connection Conn = DriverManager.getConnection("jdbc:mysql://local");
Your program can not establish a connection to the database, be sure that you have your connection URL correct.
local, should be replaced by localhost, or 127.0.0.1
You should also note, that you never actually select a database to use.

you have declared wrong connection string. please modified it according to below rule
Connection Conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/database_name");

your URL should be localhost then add the database name
have a look at this
import java.sql.DriverManager;
import java.sql.Connection;
import java.sql.SQLException;
public class JDBCExample {
public static void main(String[] argv) {
System.out.println("-------- MySQL JDBC Connection Testing ------------");
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
System.out.println("Where is your MySQL JDBC Driver?");
e.printStackTrace();
return;
}
System.out.println("MySQL JDBC Driver Registered!");
Connection connection = null;
try {
connection = DriverManager
.getConnection("jdbc:mysql://localhost:3306/mkyongcom","root", "password");
} catch (SQLException e) {
System.out.println("Connection Failed! Check output console");
e.printStackTrace();
return;
}
if (connection != null) {
System.out.println("You made it, take control your database now!");
} else {
System.out.println("Failed to make connection!");
}
}
}

MySQL JDBC error on connection

I am trying to establish a connection to remote mysql db. I have put the jar connector towar/WEB-INF/lib folder and added a library (build path).
Still I am getting this error:
java.sql.SQLException: No suitable driver found for jdbc:sql4.freemysqlhosting.net
at java.sql.DriverManager.getConnection(Unknown Source)
Here is the full code:
/**
*
*/
package com.infograph.dbconnection;
import java.sql.DriverManager;
import java.sql.Connection;
import java.sql.SQLException;
/**
* #author Vlad
*
*/
public class DBConnection
{
/**
*
*/
public DBConnection()
{
try
{
Class.forName("com.mysql.jdbc.Driver");
}
catch (ClassNotFoundException e)
{
System.out.println("Where is your MySQL JDBC Driver?");
e.printStackTrace();
return;
}
System.out.println("MySQL JDBC Driver Registered!");
Connection connection = null;
try
{
connection = DriverManager.getConnection("jdbc:sql4.freemysqlhosting.net","user", "pass");
}
catch (SQLException e1)
{
System.out.println("Connection Failed! Check output console");
e1.printStackTrace();
return;
}
if (connection != null)
{
System.out.println("You made it, take control your database now!");
}
else
{
System.out.println("Failed to make connection!");
}
}
}
What is the problem?? 10x!

I think what you meant to use is
connection = DriverManager.getConnection("jdbc:mysql://sql4.freemysqlhosting.net","user", "pass");
You possibly need to add a port number and schema name.
The URL you provided, jdbc:sql4.freemysqlhosting.net, is not valid, or at least it doesn't seem like it.

Your connection url must be in form jdbc:mysql://hostname:port/schema in order for DriverManager to determine which driver to use.
Here's more on this:
http://dev.mysql.com/doc/refman/5.0/en/connector-j-reference-configuration-properties.html

Cant connect to specific schema in mysql

i'm trying to connect with jdbc to a specific schema in mysql server, the schema name is mining
when i'm trying to connect i get access to all the DB and therefore the executing statements apply to all the schemes in my db instead only to "mining"
this is how i establish a connection:
public class Mining {
Connection conn;
void createConnection() {
try {
Class.forName("com.mysql.jdbc.Driver");
this.conn = DriverManager.getConnection(
"jdbc:mysql://localhost/?currentSchema=mining","admin","admin" );
//I ALSO TRIED THIS: "jdbc:mysql://localhost/mining","admin","admin"
} catch (SQLException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
any thoughts?
thanks!

try,
private Connection connect = DriverManager
.getConnection("jdbc:mysql://localhost/mining?"
+ "user=admin&password=admin");

String databaseURL = jdbc:mysql://hostName:portNumber/schemaName?
Connection connectionObj = DriverManager.getConnection(databaseURL,userName,password);